Biology subjects

Hojlund, A.

Publications and source records attributed to Hojlund, A..

5 recordsLinked to original sources

bioRxiv2023

Dopamine dysregulation in Parkinson's disease flattens the pleasurable urge to move to musical rhythms

The pleasurable urge to move to music (PLUMM) elicits activity in motor and reward areas of the brain and is thought to be driven by predictive processes. Dopamine within motor and limbic cortico-striatal networks is implicated in the predictive processes underlying beat-based timing and music-induced pleasure, respectively. This suggests a central role of cortico-striatal dopamine in PLUMM. This study tested this hypothesis by comparing PLUMM in Parkinsons disease patients, healthy age-matched, and young controls. Participants listened to musical sequences with varying rhythmic and harmonic complexity (low, medium, high), and rated their experienced pleasure and urge to move to the rhythm. In line with previous results, healthy younger participants showed an inverted U-shaped relation between rhythmic complexity and ratings, with a preference for medium complexity rhythms, while age-matched controls showed a similar, but weaker, inverted U-shaped response. Conversely, PD patients showed a significantly flattened response for both the urge to move and pleasure. Crucially, this flattened response could not be attributed to differences in rhythm discrimination and did not reflect an overall decrease in ratings. Together, these results support the role of dopamine within cortico-striatal networks in the predictive processes that form the link between the perceptual processing of rhythmic patterns, and the affective and motor responses to rhythmic music.

neuroscience↗

bioRxiv2021

Musicianship and melodic predictability enhance neural gain in auditory cortex during pitch deviance detection

When listening to music, pitch deviations are more salient and elicit stronger prediction error responses when the melodic context is predictable and when the listener is a musician. Yet, the neuronal dynamics and changes in synaptic efficacy underlying such effects remain unclear. Here, we employed dynamic causal modeling (DCM) to investigate whether the magnetic mismatch negativity response (MMNm)--and its modulation by context predictability and musical expertise--are associated with enhanced neural gain of auditory areas, as a plausible mechanism for encoding precision-weighted prediction errors. Using Bayesian model comparison, we asked whether models with intrinsic connections within primary auditory cortex (A1) and superior temporal gyrus (STG)--typically related to gain control--or extrinsic connections between A1 and STG--typically related to propagation of prediction and error signals--better explained magnetoencephalography (MEG) responses. We found that, compared to regular sounds, out-of-tune pitch deviations were associated with lower intrinsic (inhibitory) connectivity in A1 and STG, and lower backward (inhibitory) connectivity from STG to A1, consistent with disinhibition and enhanced neural gain in these auditory areas. More predictable melodies were associated with disinhibition in right A1, while musicianship was associated with disinhibition in left A1 and reduced connectivity from STG to left A1. These results indicate that musicianship and melodic predictability, as well as pitch deviations themselves, enhance neural gain in auditory cortex during deviance detection. Our findings are consistent with predictive processing theories suggesting that precise and informative error signals are selected by the brain for subsequent hierarchical processing. Significance statementIn complex auditory contexts, being able to identify informative signals is of paramount importance. Such is the case of music listening, where surprising sounds play a fundamental role in its perceptual, aesthetical, and emotional experience. Crucially, surprising sounds in the pitch dimension are more easily detected and generate stronger cortical responses when melodies are predictable and when the listener is a musician. Using Dynamic Causal Modelling, here we show that such effects arise from a local increase in neural gain within auditory areas, rather than from passing of prediction and error signals between brain regions. Consistent with predictive processing theories, this suggests that the enhanced precision of auditory predictive models--through melodic predictability and musical training--up-regulates the processing of informative error signals in the brain.

neuroscience↗

bioRxiv2019

Electromagnetic mapping of the effects of deep brain stimulation and dopaminergic medication on movement-related cortical activity and corticomuscular coherence in Parkinson’s disease

BackgroundParkinsons disease (PD) is a debilitating neurodegenerative disorder. PD can be treated with deep brain stimulation (DBS) when dopaminergic medication is no longer a viable option. Both treatments are effective in improving motor symptoms, however, their underlying mechanisms are not fully elucidated yet.\n\nObjectivesTo study the effects of DBS and dopaminergic medication treatments on cortical processing and corticomuscular drive during movements.\n\nMethodsMagnetoencephalography (MEG) was recorded in 10 PD patients and 10 healthy controls, performing phasic hand contractions (hand gripping). Measurements were performed in DBS-treated, untreated and dopaminergic-medicated states; healthy controls received no treatment interventions. Participants performed phasic contractions with their right hand, recorded with electromyography (EMG). Our measures of interest were beta (13-30 Hz) corticomuscular coherence (CMC) and low-gamma (31-45 Hz) power. We used Bayesian statistics on summary values from sensor space data, and we localized the sources of the effects of treatments on beta-CMC and low-gamma power using beamforming.\n\nResultsIn PD patients, DBS led to reduced CMC values, whereas dopaminergic medication increased beta-CMC values (localized to contralateral M1) to even higher levels than the controls. DBS, on the other hand, increased low-gamma power (localized to M1) compared to controls and to other conditions. Yet both treatments had similar beneficial effects on the patients motor symptoms evaluated by UPDRS-III.\n\nConclusionDespite comparable improvements from both treatments on motor symptoms, DBS and dopaminergic medication seem to have different effects on motor cortical function. This indicates that the treatments undertake different functional strategies to improve PD symptoms.

neuroscience↗

bioRxiv2019

Poorer auditory sensitivity is related to stronger visual enhancement of the human auditory mismatch negativity (MMNm)

Multisensory processing facilitates perception of our everyday environment and becomes particularly important when sensory information is degraded or close to the discrimination threshold. Here, we used magnetoencephalography and an audiovisual oddball paradigm to assess the complementary role of visual information in subtle pitch discrimination at the neural level of participants with varying levels of pitch discrimination abilities, i.e., musicians and nonmusicians. The amplitude of the auditory mismatch negativity (MMNm) served as an index of sensitivity. The gain in amplitude resulting from compatible audiovisual information was larger in participants whose MMNm amplitude was smaller in the condition deviating only in the auditory dimension, in accordance with the multisensory principle of inverse effectiveness. These findings show that discrimination of even a sensory-specific feature as pitch is facilitated by multisensory information at a pre-attentive level, and they highlight the importance of considering inter-individual differences in uni-sensory abilities when assessing multisensory processing.

neuroscience↗

bioRxiv2019

Domain-relevant auditory expertise modulates the additivity of neural mismatch responses in humans

It is unknown whether domain-relevant expertise is associated with more independent or more dependent predictive processing of acoustic features. Here, mismatch negativity (MMNm) was recorded with magnetoencephalography (MEG) from 25 musicians and 25 non-musicians, exposed to complex musical multi-feature and simple oddball control paradigms. Deviants differed in frequency (F), intensity (I), perceived location (L), or any combination of these (FI, IL, LF, FIL). Neural processing overlap was assessed through MMNm additivity by comparing double- and triple-deviant MMNms ("empirical") to summed constituent single-deviant MMNms ("modelled"). Significantly greater subadditivity was present in musicians compared to non-musicians, specifically for frequency-related deviants in complex contexts. Despite using identical sounds, expertise effects were absent from the simple paradigm. This novel finding supports the dependent processing hypothesis whereby experts recruit overlapping neural resources facilitating more integrative representations of domain-relevant stimuli. Such specialized predictive processing may enable experts such as musicians to capitalise on complex acoustic cues.

neuroscience↗